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  #31   Report Post  
Old March 13th 06, 10:33 PM posted to rec.radio.shortwave
Telamon
 
Posts: n/a
Default Something Different - On-the-Fence Loop Antenna for the Shortwave Listener (SWL)

In article ,
"HankG" wrote:

"Telamon" wrote in message
..
.
In article .com,
"RHF" wrote:

JD,

Something Different - - -
On-the-Fence Loop Antenna for the Shortwave Listener (SWL)

You should first install an 8-Ft Ground Rod at the
Foot (Base) of the new Fence.
Note - This will be the Starting and Ending Point for
your Wire Antenna Element
+ The Mounting Place for your Matching Transformer
{ A Balun = Loop-to-Coax }
+ The Connecting Point for your Coax Cable.

Start by running the Wire Antenna Element out along
the Bottom of the Fence to your Far-Point.

Then a short Wire Antenna Element Leg-Up to the
Top of the Fence.

Next run the Wire Antenna Element back along
the Top of the Fence to your Starting-Point.

Finally a a short Wire Antenna Element Down-Leg
to the Bottom of the Fence.

Mount your Matching Transformer to the Ground Rod

Connect your Coax Cable to the Matching Transformer.

Connect your Two Wire Antenna Element Ends
to the Matching Transformer.

You now have an On-the-Fence Loop Antenna
[ Bent-Around-the-Fence ]

FWIW - Two On-the-Fence Loop Antennas
One Rigged on the Fence along one Side of the Yard
One Rigged on the Fence along the Back of the Yard
Set at 90 Degress and being about 8-ft apart at their
Starting Points from a common Corner can give you
more Receiving Antenna Options.
Note - Separate Ground Rods, Baluns and Coax Cable
Feed-in-Lines are recommended if you choose to use
two On-the-Fence Loop Antennas.


Interesting. I have a fence on 2 sides of my property. Previously, I ran a
longwire along the two sides (right angle). The end closer to my house was
fed directly to my second floor receiver (no transformer or coax). This was
used primarily for LW and MW, but served as a secondary antenna for HF
(primary is Cliff Donley's 33 foot folded dipole in my roof).

As to the Question of Antenna Wire Size :
# 14 AWG Insulated Copper Wire with 19-Strands
and using PVC Insulation is cost effective and durable.
HomeDepot type - THWN or THHN in 500 Foot Spools

TIP - One of the most important details of an On-the-Fence
Antenna is the Stand-Offs used to keep the Wire "OFF"
the Fence and in the Air. TV "Stand-Offs" with Plastic
Insulator Head and 3.5" Wood Screw base hardware.
RadioShack Catalog #15-853 (4 Pack)
http://www.radioshack.com/product/in...tId=2104003&cp

Other On-the-Fence Shortwave Listener (SWL) Antenna ideas

http://groups.google.com/group/rec.r...p=rec.radio.sh
or
twave&q=on-the-fence+rhf&qt_g=1



You describe a close to the ground vertical loop antenna. I expect that
at most you would need a 2:1 BALUN but the right answer might be 1:1
with the antenna that close to the ground. The loop is balanced and the
coax is not so a BALUN is used here.

The loop is a complete antenna unlike the single wire antenna, which
still needs a counter poise to complete an RF circuit. The counterpoise
or RF return for the signal wire is the ground stake. Generally an
optimal situation would be a voltage type transformer as a UNUN so the
single wire and ground would be the primary and the coax on the
secondary. The single wire is not balanced and neither is the coax so
UNUN is used.

The loop as a complete antenna does not need the ground as a
counterpoise. Useful construction tip would be to bury the coax or if
that is not convenient then use clamp on ferrite for a RF choke to stop
noise from the radio end of the coax on the outer shield from getting to
the loop antenna then into the radio input. The clamp on ferrite would
be a current type 1:1 BALUN.


I want to replace the flimsy longwire and the 'fence loop' looks promising.
Could you (the group) comment on the use of this setup for LW, MW, and HF
(each leg is about 85 feet long) with regard to the loops vertical
polarization, and whether bending the loop at the right-angle would add or
detract from its performance.

While you're pondering, how about a vertical 'conical loop'?


85 foot a side would be a 340 foot loop with a 1 wavelength of 2.95
MHz. When the loop receives at 1 wavelength and more than one
wavelength the receive pattern is in and out of the loop plane so a
horizontal loop would look straight up. Most DX signals tend toward the
horizon so this does not work as well. This type of antenna seems to
work better during the dark hours for me and not as good during the
daytime.

Conical verticals also tend to look up. These are used in the HARP
project to receive signals during tests. I don't know of anyone using
this type for SW listening. It would be interesting to try it.

--
Telamon
Ventura, California
  #32   Report Post  
Old March 19th 06, 02:07 PM posted to rec.radio.shortwave
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

On 19 Mar 2006 03:13:22 -0800, "RHF"
wrote:

For One and All,

Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener
(SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

Top Dipole Antenna for the 31 Meter Band
- Height above ground On-the-Fence = 5-Feet
- Two 24.5 Feet long Single Wire Arms = 1/4 WL
- Tip-to-Tip Length of 49.0 Feet = 1/2 WL
- First 34 Inches for the Wire Antenna Elements
(Dipole Arms) Sloping Up at 45 Degrees from the
Matching Transformer (Balun) and then Flat.

Center {Middle} Dipole Antenna for the 49 Meter Band
- Height above ground On-the-Fence = 3-Feet
- Two 38.5 Feet long Single Wire Arms = 1/4 WL
- Tip-to-Tip Length of 77.0 Feet = 1/2 WL
- Mounting-Point for the Matching Transformer (Balun).
- Wire Antenna Elements (Dipole Arms) are Rigged Flat.

Bottom Dipole Antenna for the 22 Meter Band
- Height above ground On-the-Fence = 1-Feet
- Two 17.1 Feet long Single Wire Arms = 1/4 WL
- Tip-to-Tip Length of 34.20 Feet = 1/2 WL
- First 34 Inches for the Wire Antenna Elements
(Dipole Arms) Sloping Down at 45 Degrees from
the Matching Transformer (Balun) and then Flat.

* Requires a 4:1 Matching Transformer {Balun}

* Ground Rod located in the ground
at the Center-Point of the Dipole

* 25-75 Foot of Coax Cable Feed-in-Line

* Mount on a Fence that is at least 10 Feet
away from the House / Radio Shack.

* Use # 14 AWG Insulated Stranded Copper Wire for
the Wire Antenna Elements of all three Dipole Antennas.

TIP - For a "Receive Only" Shortwave Listener (SWL)
Antenna - Simply Staple the Wire in-place On-the-Fence.
-Or- Use Screw-In TV type Stand-Offs.

Remember with All Wire Antennas :
More Wire 'is' More Wire and nothing else is assured.
.
All are WELCOME and "Invited to Join" the
Shortwave Listener (SWL) Antenna eGroup on YAHOO !
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL ANTENNAS GROUP = http://tinyurl.com/an6tw
.
Some Say: On A Clear Day You Can See Forever.
I Believe : On A Clear Night You Can Hear Forever
. . . and Beyond , , , The BEYOND ! ! !
With a Shortwave Listening Antenna of your own making.
"If You Build It {SWL Antenna} You Will Hear Them !"
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SHORTWAVE ANTENNA FORUM = http://tinyurl.com/an6tw
.
.
. .
.

For a dipole skip the 4:1 balun - go straight to the coax or use a 1:1
unun. If you were building a folded dipole the 4:1 balun would be
more appropriate. You can ground or not ground the dipole; it is a
balanced antenna so grounding is a matter of lightning protection &
providing a path for the static electricity to drain - a better path
than draining to the radio. I guess the dipole that's 1 foot above
the ground is for 'ground wave' reception 8-}
  #33   Report Post  
Old March 20th 06, 03:01 AM posted to rec.radio.shortwave
RHF
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

How...,

1. For a dipole skip the 4:1 balun - go straight to the coax
-R- Good advise for a Ham using the Dipole for a Specific
Amateur Radio Meter Band - But for a Shortwave Listener
(SWL) who is trying to use the Dipole as a general Antenna
for All-SWL-Band reception the 4:1 Balun gives them more
Listening-ability-across-the-Bands.
REMEMBER - This is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence

2. or use a 1:1 unun.
-R- An UnUn with a Dipole ?
- - - Dipole to Twin Lead / Ladder Line = BalBal
- - - Dipole to Coax Cable = BalUn

3. If you were building a folded dipole the 4:1 balun
would be more appropriate.
-R- Again this is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only"
Tri-Band Dipole {Wire} Antenna built on a On-the-Fence
The object of the 4:1 Balun is to intergrate the Signals
developed by the Three Dipole Antenna Elements into
the Single Coax Cable Feed-in-Line and provide better
Across-the-Shortwave-Bands frequency coverage.

4. You can ground or not ground the dipole;
it is a balanced antenna so grounding is a
matter of lightning protection & providing a
path for the static electricity to drain
- a better path than draining to the radio.
-R- Lightning Protection and a Static Electricity
'drain' Path are always two good things to achieve
with any Shortwave Listener's (SWL) Antenna.

5. I guess the dipole that's 1 foot above the
ground is for 'ground wave' reception 8-}
-R- Wave Goodbye "How..."

FWIW - A Dipole On-the-Fence would not be my first
choice as a Shortwave Listener's (SWL) Antenna.
But what can you do - If the ONLY place that you can
build an Antenna is On-the-Fence ? ? ? and you don't
have the Money for a Wellbrook Loop Antenna ? ? ?
Plus someone has convinced you that the ONLY
Antenna that is worth having is a Dipole - because it
is a complete Antenna that does not require a ground
to work. - - - So now all you know is that you have to
build a Dipole Antenna and it's got to fit On-the-Fence [.]


right now i am beginning to feel a little di-pole-er - iane ~ RHF
  #34   Report Post  
Old March 20th 06, 04:06 AM posted to rec.radio.shortwave
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

On 19 Mar 2006 19:01:25 -0800, "RHF"
wrote:

How...,

1. For a dipole skip the 4:1 balun - go straight to the coax
-R- Good advise for a Ham using the Dipole for a Specific
Amateur Radio Meter Band - But for a Shortwave Listener
(SWL) who is trying to use the Dipole as a general Antenna
for All-SWL-Band reception the 4:1 Balun gives them more
Listening-ability-across-the-Bands.
REMEMBER - This is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence

I believe you are mis-applying the balun. A dipole has an inherent
impedance of around 70 ohms - if using 50 ohm coax you could use a
1.5:1 or call it close enough and use a 1:1 balun (which I previously
mis-stated as an unun) - or just go direct to the coax. As to giving
'more listenability' on other bands, well that's probably about as
debated as the 9:1 balun with end-fed wires & inverted L antennas.
One thing the balun does do is provide isolation between the antenna
and feedline and this 'decoupling' can make for a quiter antenna
system.

2. or use a 1:1 unun.
-R- An UnUn with a Dipole ?
- - - Dipole to Twin Lead / Ladder Line = BalBal
- - - Dipole to Coax Cable = BalUn

OOPS! My faux pas, should read 1:1 balun for Dipole to 75 ohm coax
cable, 1.5:1 balun for Dipole to 50 ohm coax cable. Dipole to
twinlead could be direct or use a 1:1 isolation transformer.

3. If you were building a folded dipole the 4:1 balun
would be more appropriate.
-R- Again this is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only"
Tri-Band Dipole {Wire} Antenna built on a On-the-Fence
The object of the 4:1 Balun is to intergrate the Signals
developed by the Three Dipole Antenna Elements into
the Single Coax Cable Feed-in-Line and provide better
Across-the-Shortwave-Bands frequency coverage.

The balun will not necessarily 'integrate the signals', in other than
a 1:1 configuration it transforms impedance and allows you to go from
balanced to unbalanced line. At some frequencies it may 'smooth out'
the impedance mismatch, however if you want to combine the signals a
triplexer would do the trick.

4. You can ground or not ground the dipole;
it is a balanced antenna so grounding is a
matter of lightning protection & providing a
path for the static electricity to drain
- a better path than draining to the radio.
-R- Lightning Protection and a Static Electricity
'drain' Path are always two good things to achieve
with any Shortwave Listener's (SWL) Antenna.

Agreed.

5. I guess the dipole that's 1 foot above the
ground is for 'ground wave' reception 8-}
-R- Wave Goodbye "How..."

Nope, not goodbye yet.......I'd like to rebut your rebuttal.......

FWIW - A Dipole On-the-Fence would not be my first
choice as a Shortwave Listener's (SWL) Antenna.
But what can you do - If the ONLY place that you can
build an Antenna is On-the-Fence ? ? ? and you don't
have the Money for a Wellbrook Loop Antenna ? ? ?
Plus someone has convinced you that the ONLY
Antenna that is worth having is a Dipole - because it
is a complete Antenna that does not require a ground
to work. - - - So now all you know is that you have to
build a Dipole Antenna and it's got to fit On-the-Fence [.]


right now i am beginning to feel a little di-pole-er - iane ~ RHF
.

RHF - Granted, a fence mounted antenna is the best some folks can do;
there are other options to the dipole such as an end-fed or a
fence-loop; the former requiring a ground the latter not. Might I
suggest to you the ARRL Antenna Book (not the end-all to antenna
knowledge but a good start; it has a section on coupling the antenna
to the feedline. They explain what I was trying to say in my original
response to you in a better fashion than I can. They even describe a
1:1 balun which is what I mis-stated as an unun. Though you (and many
participants here) are mainly interested in receive-only antennas; the
principles apply equally to antennas used for transmit and receive.
If you don't have a current copy of this ARRL publication see if you
can get your hands on a used one - the physics haven't changed from
year to year. What you have described will work, no doubt about it -
but wouldn't you like to explore ways to make things work better?

Howard
  #35   Report Post  
Old March 20th 06, 10:23 PM posted to rec.radio.shortwave
Bob Miller
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

On 19 Mar 2006 19:01:25 -0800, "RHF"
wrote:

A 72-ohm fanned dipole connected to a single coax feed going to a
50-ohm input doesn't need a balun, especially a 4-1 jobbie.

bob
k5qwg

How...,

1. For a dipole skip the 4:1 balun - go straight to the coax
-R- Good advise for a Ham using the Dipole for a Specific
Amateur Radio Meter Band - But for a Shortwave Listener
(SWL) who is trying to use the Dipole as a general Antenna
for All-SWL-Band reception the 4:1 Balun gives them more
Listening-ability-across-the-Bands.
REMEMBER - This is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence

2. or use a 1:1 unun.
-R- An UnUn with a Dipole ?
- - - Dipole to Twin Lead / Ladder Line = BalBal
- - - Dipole to Coax Cable = BalUn

3. If you were building a folded dipole the 4:1 balun
would be more appropriate.
-R- Again this is a Three Band : 49 & 31 & 22 Meter
Bands Shortwave Listener (SWL) "Receive Only"
Tri-Band Dipole {Wire} Antenna built on a On-the-Fence
The object of the 4:1 Balun is to intergrate the Signals
developed by the Three Dipole Antenna Elements into
the Single Coax Cable Feed-in-Line and provide better
Across-the-Shortwave-Bands frequency coverage.

4. You can ground or not ground the dipole;
it is a balanced antenna so grounding is a
matter of lightning protection & providing a
path for the static electricity to drain
- a better path than draining to the radio.
-R- Lightning Protection and a Static Electricity
'drain' Path are always two good things to achieve
with any Shortwave Listener's (SWL) Antenna.

5. I guess the dipole that's 1 foot above the
ground is for 'ground wave' reception 8-}
-R- Wave Goodbye "How..."

FWIW - A Dipole On-the-Fence would not be my first
choice as a Shortwave Listener's (SWL) Antenna.
But what can you do - If the ONLY place that you can
build an Antenna is On-the-Fence ? ? ? and you don't
have the Money for a Wellbrook Loop Antenna ? ? ?
Plus someone has convinced you that the ONLY
Antenna that is worth having is a Dipole - because it
is a complete Antenna that does not require a ground
to work. - - - So now all you know is that you have to
build a Dipole Antenna and it's got to fit On-the-Fence [.]


right now i am beginning to feel a little di-pole-er - iane ~ RHF
.
.
. .
.



  #36   Report Post  
Old March 21st 06, 07:14 AM posted to rec.radio.shortwave
RHF
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

Howard,

1. One thing the balun does do is provide isolation
between the antenna and feedline and this 'decoupling'
can make for a quiter antenna system.
-R- On this we can agree.

2. The balun will not necessarily 'integrate the signals',
in other than a 1:1 configuration it transforms impedance
and allows you to go from balanced to unbalanced line.
At some frequencies it may 'smooth out' the impedance
mismatch, however if you want to combine the signals a
triplexer would do the trick.
-R- Yes - The Balun would simply 'smooth out' the
impedance mismatch between the combined Dipole
Antenna Elements and the Coax Cable Feed-in-Line.
- - - I have often though that a Bal(3)Un(1) for these
types of Multi-Band (Multi-Element) type of 'combined'
Antennas would be a better Matching Device.
? WHAT ? For the Three Dipole Antenna with One Coax
Cable Feed-in-Line :
* Three separate Primary Windings of 30 Turns
# 1 - One for the 49m Dipole Wire Antenna Element
# 2 - One for the 31m Dipole Wire Antenna Element
# 3 - One for the 22m Dipole Wire Antenna Element
* One Secondary Winding of 10 Turns for the Coax
Cable Feed-in-Line.
With All Four (4) Windings on a Single Ferrite Core.

3. ARRL Antenna Book
-R- Books are wonderful and I do own a few books.
But in the media of the NewsGroups (RRS) a
WebPage (Link) that provides some information
and Insight and is more directly accessable by
most readers here. Plus my personal 'theme'
here is to Keep It Simple And Practical (KISAP)
with some basic "How To" Details (Description).

that's where i am coming from - iane ~ RHF
  #37   Report Post  
Old March 22nd 06, 03:41 AM posted to rec.radio.shortwave
RHF
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

BM [K5QWG],

What you say is correct if the Fan Dipole is being
used properly as a Single Band Amateur Antenna.

How Ever ! ! ! ) Take the same Antenna and . . .
[ Remember we have an Antenna built On-the-Fence
and for what ever reason {or lack of understanding}
the Shortwave Listener (SWL) has decided the a
Dipole is the only thing {Antenna} that they want.
Plus the want a Mutli-Band Antenna to cover a few
of the Shortwave Bands for Broad-Cast Program
Listening (BCL) ]

SO HERE WE GO AGAIN - - - - - - - - - - - - - -
This is a Three Band : 49 & 31 & 22 Meter Bands
Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence
Question What Do We Do To Make It 'perfrom' ? ? ?
? To Perform - Or Not To Perform - - - Is That a Question ?
A little better across the Shortwave Bands so we can
"HEAR" a little of everything from 1.8 MHz to 30 MHz.
Not a good answer but never the less a fair answer is
the 4:1 Balun to 'smooth-out' the impedance mismatches
from the Three (3) Dipole Antenna Elements and provide
a fair 'match' from the three of them across the Shortwave
Bands; know that they are One-Foot, Three-Feet and
Five-Feet above the ground when Idealy they would be :
49m = 38.5 Feet above AGL
31m = 24.5 Feet above AGL
22m = 17.1 Feet above AGL

alas - it is an imperfect world - iane ~ RHF
  #38   Report Post  
Old March 22nd 06, 05:02 PM posted to rec.radio.shortwave
Bob Miller
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

On 21 Mar 2006 19:41:42 -0800, "RHF"
wrote:


SO HERE WE GO AGAIN - - - - - - - - - - - - - -
This is a Three Band : 49 & 31 & 22 Meter Bands
Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence
Question What Do We Do To Make It 'perfrom' ? ? ?
? To Perform - Or Not To Perform - - - Is That a Question ?
A little better across the Shortwave Bands so we can
"HEAR" a little of everything from 1.8 MHz to 30 MHz.
Not a good answer but never the less a fair answer is
the 4:1 Balun to 'smooth-out' the impedance mismatches
from the Three (3) Dipole Antenna Elements and provide
a fair 'match' from the three of them across the Shortwave
Bands; know that they are One-Foot, Three-Feet and
Five-Feet above the ground when Idealy they would be :
49m = 38.5 Feet above AGL
31m = 24.5 Feet above AGL
22m = 17.1 Feet above AGL

alas - it is an imperfect world - iane ~ RHF
.
.
. .


I took into consideraton that there are three dipoles here, connected
to a single transmission line -- so hopefully each will be within
yelling distance, impedance wise, of 75 ohms, so there's no need for a
4-1 balun to a 50 ohm input.

Unless you want to transpose 75 ohms to about 20 ohms?

And if the antenna is less than a half-wavelength high at frequency,
on a fence so to speak, the impedance could be anywhere between 40 and
90 ohms, according to chap. 20 of the ARRL handbook. Still no need for
a 4-1 balun. Maybe a 1 to 1 choke balun, to sop up noise, but a 4-1?

What is it, this high religious SW fever for baluns in this group :-)

bob
k5qwg

  #39   Report Post  
Old March 22nd 06, 09:01 PM posted to rec.radio.shortwave
Telamon
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

In article ,
Bob Miller wrote:

On 21 Mar 2006 19:41:42 -0800, "RHF"
wrote:


SO HERE WE GO AGAIN - - - - - - - - - - - - - -
This is a Three Band : 49 & 31 & 22 Meter Bands
Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence
Question What Do We Do To Make It 'perfrom' ? ? ?
? To Perform - Or Not To Perform - - - Is That a Question ?
A little better across the Shortwave Bands so we can
"HEAR" a little of everything from 1.8 MHz to 30 MHz.
Not a good answer but never the less a fair answer is
the 4:1 Balun to 'smooth-out' the impedance mismatches
from the Three (3) Dipole Antenna Elements and provide
a fair 'match' from the three of them across the Shortwave
Bands; know that they are One-Foot, Three-Feet and
Five-Feet above the ground when Idealy they would be :
49m = 38.5 Feet above AGL
31m = 24.5 Feet above AGL
22m = 17.1 Feet above AGL


I took into consideraton that there are three dipoles here, connected
to a single transmission line -- so hopefully each will be within
yelling distance, impedance wise, of 75 ohms, so there's no need for a
4-1 balun to a 50 ohm input.

Unless you want to transpose 75 ohms to about 20 ohms?

And if the antenna is less than a half-wavelength high at frequency,
on a fence so to speak, the impedance could be anywhere between 40 and
90 ohms, according to chap. 20 of the ARRL handbook. Still no need for
a 4-1 balun. Maybe a 1 to 1 choke balun, to sop up noise, but a 4-1?

What is it, this high religious SW fever for baluns in this group :-)


It's a way to current terminate a coax so it is not completely (100%)
dependent on the the antenna impedance for the source termination.

You want to have lengths of the dipoles to be high impedance respective
to each other so the characteristic impedance of the sum says around the
72 to 50 ohm range. You would then want to then use a 1:1 BALUN.

--
Telamon
Ventura, California
  #40   Report Post  
Old March 24th 06, 04:12 AM posted to rec.radio.shortwave
toTaLhAt
 
Posts: n/a
Default Three Band : 49 & 31 & 22 Meter Bands Shortwave Listener (SWL) Tri-Band Dipole {Wire} Antenna On-the-Fence

On Wed, 22 Mar 2006 21:01:37 GMT, Telamon
wrote:

In article ,
Bob Miller wrote:

On 21 Mar 2006 19:41:42 -0800, "RHF"
wrote:


SO HERE WE GO AGAIN - - - - - - - - - - - - - -
This is a Three Band : 49 & 31 & 22 Meter Bands
Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence
Question What Do We Do To Make It 'perfrom' ? ? ?
? To Perform - Or Not To Perform - - - Is That a Question ?
A little better across the Shortwave Bands so we can
"HEAR" a little of everything from 1.8 MHz to 30 MHz.
Not a good answer but never the less a fair answer is
the 4:1 Balun to 'smooth-out' the impedance mismatches
from the Three (3) Dipole Antenna Elements and provide
a fair 'match' from the three of them across the Shortwave
Bands; know that they are One-Foot, Three-Feet and
Five-Feet above the ground when Idealy they would be :
49m = 38.5 Feet above AGL
31m = 24.5 Feet above AGL
22m = 17.1 Feet above AGL


I took into consideraton that there are three dipoles here, connected
to a single transmission line -- so hopefully each will be within
yelling distance, impedance wise, of 75 ohms, so there's no need for a
4-1 balun to a 50 ohm input.

Unless you want to transpose 75 ohms to about 20 ohms?

And if the antenna is less than a half-wavelength high at frequency,
on a fence so to speak, the impedance could be anywhere between 40 and
90 ohms, according to chap. 20 of the ARRL handbook. Still no need for
a 4-1 balun. Maybe a 1 to 1 choke balun, to sop up noise, but a 4-1?

What is it, this high religious SW fever for baluns in this group :-)


It's a way to current terminate a coax so it is not completely (100%)
dependent on the the antenna impedance for the source termination.

You want to have lengths of the dipoles to be high impedance respective
to each other so the characteristic impedance of the sum says around the
72 to 50 ohm range. You would then want to then use a 1:1 BALUN.



H-Y-P-O-C-R-I-T-E ALERT!!
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